Apparatus and methods for creating a venous valve from autologous tissue

ABSTRACT

An implantable prosthesis for percutaneous placement within a vein that forces opposing portions of the vessel wall of a vein together to create a new valve of autologous vein tissue to be operable to alternate between a valve closed configuration and a valve open configuration. When in a preset closed configuration, the implantable prosthesis pushes or pulls portions of the vessel wall of the vein together to substantially close the vein lumen and prevent retrograde blood flow from backflowing through the new valve in the valve closed configuration. The implantable prosthesis has leg portions that may be pushed apart in response to antegrade blood flow through the vein to allow the new valve to achieve the valve open configuration.

FIELD OF THE INVENTION

The invention relates to apparatus and methods for percutaneouslycreating a one-way venous valve in vivo from autologous tissue.

BACKGROUND OF THE INVENTION

Venous valves are found within native venous vessels and are used toassist in returning blood back to the heart in an antegrade directionfrom all parts of the body. The venous system of the leg for exampleincludes the deep venous system and the superficial venous system, bothof which are provided with venous valves which are intended to directblood toward the heart and prevent backflow or retrograde flow which canlead to blood pooling or stasis in the leg. Incompetent valves can alsolead to reflux of blood from the deep venous system to the superficialvenous system and the formation of varicose veins. Superficial veinswhich include the greater and lesser saphenous veins have perforatingbranches in the femoral and popliteal regions of the leg that directblood flow toward the deep venous system and generally have a venousvalve located near the junction with the deep system. Deep veins of theleg include the anterior and posterior tibial veins, popliteal veins,and femoral veins. Deep veins are surrounded in part by musculaturetissues that assist in generating flow due to muscle contraction duringnormal walking or exercising. Venous pressure in lower leg veins of ahealthy person may range from 0 mm Hg to over 200 mm Hg, depending onfactors such as the activity of the body, i.e., stationary orexercising, the position of the body, i.e., supine or standing, and thelocation of the vein, i.e., ankle or thigh. For example, venous pressuremay be approximately 80-90 mm Hg while standing and may be reduced to60-70 mm Hg during exercise. Despite exposure to such pressures, thevalves of the leg are very flexible and can close with a pressure dropof less than one mm Hg.

FIGS. 1A-1B are schematic representations of blood flow through ahealthy native valve 104 within a vein 100. Valves within the venoussystem are configured in a variety of shapes that depend on anatomicallocation, vessel size, and function. For example, the shape of thevenous valve may include leaflets or leaflets with sinuses. The naturalvenous valve leaflet configuration referenced herein is for clarity offunction and is not limiting in the application of the referencedembodiments. Venous valve 104 controls blood flow through lumen 102 ofvein 100 via leaflets 106, 108. More particularly, venous valve 104opens to allow antegrade flow 112 through leaflets 106, 108 as shown inFIG. 1A. Venous valve 104 closes to prevent retrograde flow or backflow114 through leaflets 106, 108 as shown in FIG. 1B.

Veins typically located in the leg can become distended from prolongedexposure to excessive pressure and due to weaknesses found in the vesselwall causing the natural venous valves to become incompetent leading toretrograde blood flow in the veins. Such incompetent valves no longerfunction to help pump or direct the blood back to the heart duringnormal walking or use of the leg muscles. As a result, blood tends topool in the lower leg and can lead to leg swelling and the formation ofdeep venous thrombosis and phlebitis. The formation of thrombus in theveins can further impair venous valvular function by causing valvularadherence to the venous wall with possible irreversible loss of venousfunction. Continued exposure of the venous system to blood pooling andswelling of the surrounding tissue can lead to post phlebitic syndromewith a propensity for open sores, infection, and may lead to limbamputation.

Chronic Venous Insufficiency (CVI) occurs in patients that have deep andsuperficial venous valves of their lower extremities (distal to theirpelvis) that have failed or become incompetent due to congenitalvalvular abnormalities and/or pathophysiologic disease of thevasculature. As a result, such patients suffer from varicose veins,swelling and pain of the lower extremities, edema, hyper pigmentation,lipodermatosclerosis, and deep vein thrombosis (DVT). Such patients areat increased risk for development of soft tissue necrosis, ulcerations,pulmonary embolism, stroke, heart attack, and amputations.

FIG. 2 is a schematic representation of blood flow through anincompetent venous valve. Valve leaflets 106, 108 do not completelyclose and thus allow some venous blood to flow in a retrogradedirection. The backflow 114 leaks through venous valve 104 creatingblood build-up that eventually may destroy the venous valve and cause adistended area or venous wall bulge 110. More specifically, the vesselwall of vein 100 expands into a pouch or bulge, such that the vessel hasa knotted appearance when the pouch is filled with blood. As the bulgingprogresses, vein 100 becomes further enlarged and valve leaflets 106,108 move farther apart, allowing even more blood to backflow. Thus, oncevalve 104 becomes incompetent, the venous insufficiency/incompetencyprogressively worsens. The distended vessel wall area may occur on theoutflow side of the valve above leaflets 106, 108 as shown in FIG. 2,and/or on the inflow side of the valve below leaflets 106, 108. After avein segment becomes incompetent, the vessel wall dilates and fluidvelocity there through decreases, which may lead to flow stasis andthrombus formation in the proximity of the venous valve.

Repair and replacement of venous valves presents a formidable challengedue to the low blood flow rate found in native veins, the very thin wallstructure of the venous wall and the venous valve, and the ease andfrequency of which venous blood flow can be impeded or totally blockedfor a period of time. Surgical reconstruction techniques used to addressvenous valve incompetence include venous valve bypass using a segment ofvein with a competent valve, venous transposition to bypass venous bloodflow through a neighboring competent valve, and valvuloplasty to repairthe valve cusps. These surgical approaches may involve placement ofsynthetic, allograft and/or xenograft prostheses inside of or around thevein. However, such prostheses have not been devoid of problems, such asthrombus formation and valve failure due to leafletthickening/stiffening, non-physiologic flow conditions,non-biocompatible materials and/or excessive dilation of the vesselswith a subsequent decrease in blood flow rates. In addition, many venousvalve prostheses include leaflets and/or hinged flaps and are similar tovalves placed into the heart, which are complex and designed for highblood pressures and flow associated with the heart instead of lowervenous blood pressures and flow associated with veins in the lowerextremities.

Percutaneous methods for treatment of venous insufficiency are beingstudied, some of which include placement of synthetic, allograft and/orxenograft prosthesis that suffer from similar problems as the surgicallyimplanted ones discussed above.

In addition, venous valve formation from autologous tissue has beendisclosed in U.S. Pat. No. 6,902,576 to Drasler et al. Drasler et al.suggests use of autologous tissue with blood contact of an endotheliallayer to eliminate biocompatability issues and also alleviate thrombusformation due to low flow. However, methods of in situ venous valveformation according to Drasler et al. are surgical in nature and involvere-shaping a distended, diseased vein, which carries with it the risk ofrupture or tearing of the thin-walled structure.

In light of these limitations, there is a need for an improved device torestore normal venous circulation to patients suffering from venousvalve insufficiency. The present disclosure is directed to a simpleprosthesis that may be used in percutaneous, minimally invasiveprocedures to create a venous valve in vivo from autologous vein tissue.

BRIEF SUMMARY OF THE INVENTION

Embodiments hereof are directed to an implantable prosthesis forcreating a venous valve of autologous tissue. In a preset closedconfiguration, the prosthesis forces opposing portions of a vein walltogether to create a valve of autologous vein tissue to substantiallyprevent retrograde blood flow through the valve. The prosthesis assumesa temporary open configuration in response to antegrade blood flowthrough the vein.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following description of embodiments thereof asillustrated in the accompanying drawings. The accompanying drawings,which are incorporated herein and form a part of the specification,further serve to explain the principles of the invention and to enable aperson skilled in the pertinent art to make and use the invention. Thedrawings are not to scale.

FIGS. 1A-1B are schematic representations of blood flow through ahealthy valve within a vein.

FIG. 2 is a schematic representation of blood flow through anincompetent valve within a vein.

FIG. 3 is a perspective view of a valve creation device according to anembodiment hereof.

FIG. 4 is a schematic representation of the valve creation device ofFIG. 3 implanted within a vein, wherein the valve creation device is inits closed or preset configuration.

FIG. 4A is a cross-sectional view taken along line A-A of FIG. 4.

FIG. 5 is a schematic representation of the valve creation device ofFIG. 3 implanted within a vein, wherein the valve creation device is inits open configuration.

FIG. 5A is a cross-sectional view taken along line A-A of FIG. 5.

FIG. 6 is a perspective view of a valve creation device according toanother embodiment hereof.

FIG. 7 is a perspective view of a valve creation device according toanother embodiment hereof.

FIG. 8A is a side view of the valve creation device of FIG. 7 implantedwithin a vein.

FIG. 8B is a top view of the valve creation device of FIG. 7.

FIG. 9 is a side view of a portion of a valve creation device accordingto another embodiment hereof.

FIG. 10 is a schematic representation of a valve creation deviceaccording to another embodiment hereof, wherein the device is implantedwithin a vein and is in its closed or preset configuration.

FIG. 11 is a schematic representation of the valve creation device ofFIG. 10 implanted within a vein, wherein the valve creation device is inits open configuration.

FIG. 12 is a perspective view of a valve creation device according toanother embodiment hereof wherein the valve creation device is in theopen configuration.

FIG. 13 is a cross-sectional view of the valve creation device of FIG.12 placed within a vein, wherein the valve creation device is in theopen configuration.

FIG. 13A is a schematic representation of the valve creation device ofFIG. 12 placed within a vein, wherein the valve creation device is inthe open configuration.

FIGS. 14, 15, 16, and 17 are schematic representations of a method ofpercutaneously placing a valve creation device within a vein to create avalve from autologous vein tissue according to an embodiment hereof.

FIG. 14A and FIG. 14 are schematic representations of alternateconfigurations for the delivery system of FIGS. 14-17 according to anembodiment hereof.

FIGS. 18, 19, and 20 are schematic representations of another method ofpercutaneously placing a valve creation device within a vein to create avalve from autologous vein tissue according to an embodiment hereof.

FIG. 18A is an end view of the delivery system of FIGS. 18 and 19, withthe legs of the valve creation device loaded therein.

FIG. 18B is a perspective view of the delivery system of FIGS. 18 and19, with the valve creation device loaded therein.

FIGS. 21-24 are schematic representations of a method of percutaneouslyplacing the valve creation device of FIGS. 10-11 within a vein to createa valve from autologous vein tissue according to an embodiment hereof.

FIGS. 25A and 25B are perspective views of a valve creation deviceaccording to another embodiment hereof.

FIG. 26 is a schematic representation of a valve creation deviceaccording to another embodiment hereof.

FIG. 27 is a schematic representation of a valve creation deviceaccording to another embodiment hereof.

DETAILED DESCRIPTION OF THE INVENTION

Specific embodiments of the present invention are now described withreference to the figures, wherein like reference numbers indicateidentical or functionally similar elements. The terms “distal” and“proximal” are used in the following description with respect to aposition or direction relative to the treating clinician. “Distal” or“distally” are a position distant from or in a direction away from theclinician. “Proximal” and “proximally” are a position near or in adirection toward the clinician.

The following detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. Although the description of the invention is in the contextof treatment of blood vessels such as the veins, the invention may alsobe used in any other body passageways where it is deemed useful.Furthermore, there is no intention to be bound by any expressed orimplied theory presented in the preceding technical field, background,brief summary or the following detailed description.

Referring to FIGS. 3-5, an implantable prosthesis or valve creationdevice 316 for treating chronic venous insufficiency according to anembodiment hereof is shown. In creating a valve that controls the flowof blood through a vein from autologous vein tissue, valve creationdevice 316 may be considered a scaffolding or support framework thatopens and closes opposing portions of the vessel wall in response toantegrade and retrograde blood flow, i.e., pressure differentials acrossthe newly created valve, to mimic venous valve operation. Valve creationdevice 316 is an implantable prosthesis formed from a wire-like ortubular structure 317 of a biocompatible resilient material such asnitinol, 316L stainless steel, MP35N spring wire, an acetal copolymer,or a polymeric material having shape memory characteristics. In variousembodiments in accordance herewith, wire-like structure 317 may be solidor hollow and have a circular cross-section. By minimizing thecross-section of wire-like structure 317, the amount of foreign materialimplanted in the body and the interruption or footprint of the implantrelative to blood flow is minimized to avoid thrombosis. In oneembodiment, wire-like structure 317 has a diameter less than 0.10inches. In one embodiment, wire-like structure 317 has a diameterbetween 0.006 inches-0.040 inches. In another embodiment, thecross-section of wire-like structure 317 may be an oval, square,rectangular, or any other suitable shape.

Wire-like structure 317 is shaped to include a first leg 318, a secondleg 322, and a biasing member 326 extending from first leg 318 to secondleg 322. As shown in FIG. 3, biasing member 326 is a curved segmentintegrally formed with and positioned between first leg 318 and secondleg 322 such that valve creation device 316 is a unitary structureformed out of a single piece of material. Biasing member 326 biasesfirst leg 318 and second leg 322 towards each other due to thematerial's inherent spring restorative forces. In an embodiment, biasingmember 326 may be U-shaped and legs 318, 322 may be mirror images ofeach other. In another embodiment, the valve creation device may includea biasing member that is a separate component that is attached to thefirst and second legs by any suitable manner known in the art such asfor example welding, including resistance welding, friction welding,laser welding or another form of welding, soldering, using an adhesive,adding a connecting element there between, or by another mechanicalmethod. Rather than an arc or curved segment, the biasing member mayhave alternative configurations that bias first leg 318 and second leg322 towards each other and impart spring characteristics to the valvecreation device. For example, FIG. 26 illustrates a valve creationdevice 2616 resembling a binder clip having an elongated biasing member2626 extending from a first leg 2618 to a second leg 2622. The roundedcorners or ends 2626A, 2626B of biasing member 2626 straddle or spanacross the vessel lumen of the vein in situ. In another example shown inFIG. 27, a valve creation device 2716 has a looped biasing member 2726connecting a first leg 2718 to a second leg 2722. In another embodiment(not shown), the biasing member may be an asymmetric curved segment suchthat the valve creation device resembles a bobby pin.

In the embodiment shown in FIG. 3, end portions 320, 324 of first andsecond legs 318, 322, respectively, include sharpened or pointed tips328, 330, respectively, that are operable to pierce and penetratethrough opposing portions of the vessel wall of a vein. In addition, endportions 320, 324 may be curved or hooked as shown to secure valvecreation device 316 within the vein. The hooked configuration ensuresthat end portions 320, 324 remain on the outer or exterior surface ofthe vein wall and prevent tips 328, 330 from incidentally becomingdislodged and/or pushed into the vein resulting in a possibleembolization. More specifically, hooked end portions 320, 324 areintended to prevent valve creation device 316 from being pushed out ofposition by the antegrade flow passing across the portion of valvecreation device 316 in the lumen.

Wire-like structure 317 is formed from a biocompatible resilientmaterial and has an inherent spring restorative force or mechanicalmemory to return to its original preset shape, shown in FIG. 3, afterbeing loaded. “Resilient” and “resilience” as used herein to refer to amaterial that is capable of recovering an original preset shape or formafter being elastically stretched, deformed, compressed, or the like.Valve creation device 316 is operable to alternate between the presetclosed configuration shown in FIG. 3, which when implanted creates avalve closed configuration as shown in FIGS. 4 and 4A, and an openconfiguration, which when subjected to antegrade flow in situ creates avalve open or flow configuration as shown in FIGS. 5 and 5A. Mechanicalmemory may be imparted to wire-like structure 317 by thermal treatmentto achieve a spring temper in stainless steel, for example, or to set ashape memory in a susceptible metal alloy, such as nitinol. For example,wire-like structure 317 of valve creation device 316 may be shape-setinto the closed configuration using an oven set to an appropriatetemperature for the material, by e.g., approximately 525° C. for nitinolalthough the temperature will vary depending on the material ofwire-like structure 317. When valve creation device 316 is in the presetclosed configuration, a contact portion 319 of first leg 318 and acontact portion 323 of second leg 322 are biased or pressed toward eachother due to biasing member 326, such that when valve creation device316 is implanted within a vein as further described below the valvecreation device will operably force opposing sites or points on thevessel wall of a vein together to create a new valve of autologous veintissue. In another embodiment hereof (not shown), in the preset closedconfiguration, contact portion 319 of first leg 318 may pass over oroverlap contact portion 323 of second leg 322 to operably force opposingsites on the vessel wall of a vein together. In situ, antegrade bloodflow acts against the new valve, overcomes the spring restorative forceof wire-like structure 317, and forces contact portions 319, 323 ofvalve creation device 316 apart to achieve the valve open configurationof FIG. 5 that allows blood flow through the new valve. When blood flowthrough the vein changes direction, i.e., antegrade blood flow andpressure is reduced and retrograde blood flow occurs due to changingpressure differentials across the new valve, the spring restorativeforce of wire-like structure 317 takes over and causes valve creationdevice 316 to revert back to the preset closed configuration to therebyachieve the valve closed configuration of FIG. 4 that prevents bloodfrom backflowing through the new valve. The relatively simpleconstruction of valve creation device 316 does not include leaflets orhinged flaps that may thicken, tear or fail, avoids tissue ingrowth ofsuch leaflets, and also avoids pooling of blood within such leafletsthat may result in clots.

More particularly, FIGS. 4, 4A, 5 and 5A are schematic representationsof how valve creation device 316 forms a new venous valve fromautologous tissue and alternates between its preset closed configurationand its open configuration to regulate blood flow through the new venousvalve. FIG. 4 is a schematic view of valve creation device 316 in itspreset closed configuration placed within a vein 400 having anincompetent native valve (not shown). Valve creation device 316 isdelivered to and deployed within vein 400 in a percutaneous manner, aswill be described in more detail below, and is positioned at a targetlocation within lumen 402 of vein 400 where a new vein valve is to becreated. Initially luminal access to a desired peripheral vein 400, suchas the greater or lesser saphenous, femoral, or popliteal veins, isobtained using standard percutaneous techniques. It should be understoodby one of skill in the art that methods as described herein may be usedto form an autologous valve in any vein suffering from chronic venousinsufficiency, including but not limited to superficial veins and deepveins. As shown in FIG. 4, valve creation device 316 is not required tobe placed adjacent to the incompetent valve but rather may be implantedat any location along vein 400. However, in an embodiment, the targetlocation may be adjacent to the valve leaflets of the incompetent valve.

FIG. 4 illustrates how valve creation device 316 utilizes autologousvein tissue to form a new valve by forcing together the opposingportions of the vessel wall. Once implanted, contact portion 319 ofvalve creation device 316 engages the outer surface of a vessel wall ofvein 400 at a first location, and contact portion 323 of valve creationdevice 316 engages the outer surface of the vessel wall of vein 400 atan opposing location of the vein, or approximately 180 degrees away fromthe first location. Particularly, sharpened or pointed tips 328, 330 atthe ends of wire-like structure 317 pierce and penetrate throughopposing portions of the vessel wall of vein 400. As shown in thecross-section of FIG. 4A, contact portion 319 and contact portion 323move toward each other and exert a clamping or pinching force onto theopposing walls of vein 400 to press the opposing walls of vein 400together and substantially closes lumen 402 of vein 400, therebypreventing or at least significantly reducing retrograde blood flow orreflux. The configuration, length, and width of contact portions 319,323 determine how much of the vein wall is forced together.

Once implanted in vein 400, the new valve created by valve creationdevice 316 operates as a one-way valve that allows blood to flow in anantegrade direction and controls backflow through lumen 402 of vein 400,thereby seamlessly replacing the role of an incompetent native valve. Inits closed configuration shown in FIG. 4, valve creation device 316firmly forces opposing portions of the vein wall together to preventgravitational or retrograde blood flow R_(F) from backflowing throughthe newly created valve. In an embodiment, valve creation device 316 canwithstand backpressure, i.e., a pressure gradient in the proximal todistal direction, of 300 mmHg with less than 1.0 mL/min of leakage. Whenantegrade blood flow A_(F) overcomes the biasing spring force ormechanical memory of valve creation device 316 and pushes or forcesapart contact portions 319, 323 of valve creation device 316, the newvalve achieves the open valve configuration shown in FIGS. 5 and 5A andantegrade blood flows through the new valve. More particularly, bloodflow pressure builds up on the inflow or distal side of the new valvewhen it is in the closed configuration shown in FIG. 4 until the pointat which the pressure pushing outward against the inside surfaces orwalls of the vessel exceeds the closing biasing force of valve creationdevice 316 pushing against the outer surface of the vessel. Valvecreation device 316 then opens up, allowing the vein walls to separateand blood to flow antegrade across the new valve. The movement ofantegrade blood flow across the new valve results in a drop or relief ofpressure, and the biasing spring force or mechanical memory of valvecreation device 316 takes over and closes valve creation device 316 thuspreventing the backflow of blood.

More specifically, in order for blood to flow through a venous valve,there must be a force propelling the blood. This force is the pressuregradient or differential ΔP, which is the difference in blood pressureoccurring across the valve between the inflow or distal side of thevalve and the outflow or proximal side of the valve. When pumped bloodis advanced through vein 400 during normal circulation, the pressuregradient driving venous blood flow back to the heart is quite low.Native venous valves typically open with less than a 5 mm Hg pressuregradient. Thus, valve creation device 316 preferably opens under thesame pressure gradients. In an embodiment, valve creation device 316 isforced into the open configuration in which the device is sufficientlyspread apart to allow blood flow through the new valve and consequentlylumen 402 of vein 400 in response to a 5 mm Hg pressure gradient. Inanother embodiment, valve creation device 316 opens in response to a 2mmHg pressure gradient. Under certain higher pressure gradients, valvecreation device 316 may significantly spread apart such that the newvalve approaches a tubular or cylindrical cross-section. However,contact portions 319, 323 of valve creation device 316 need only beradially separated to a point sufficient to allow flow through the newvalve, i.e., vein 400, and thus the new valve may have an hourglassshape when valve creation device 316 is in the open configuration.Generally, valve creation device 316 will achieve a valve openconfiguration that permits a flow of blood through the new valve at arate of about 0.25 L/min to about 5 L/min.

In the embodiment depicted in FIGS. 3-4 having contact portions 319, 323located at opposing locations within the vein, valve creation device 316has a substantially flat longitudinally extending structure whenpositioned in the vein. However, in another embodiment shown in FIGS.25A and 25B, a valve creation device 2516 has a substantially conicalstructure when in the open configuration by including multiple V-shapedwire-like structures 2517A, 2517B, and 2517C, each having closed andopen configurations similar to wire-like structure 317 as describedabove. Wire-like structures 2517A, 2517B, and 2517C are oriented suchthat three sets of contact portions are located around the circumferenceof the vein. The multiple wire-like structures are secured together atleast at a single overlapping point or apex 2515 on the biasing members.With three sets of contact portions positioned around the circumferenceof the vein more complete closure of the lumen of the vein may be hadwhen the opposing portions of the vessel wall are forced or gatheredtogether by each wire-like structure 2517A, 2517B, and 2517C of valvecreation device 2516. Although FIGS. 25A and 25B illustrate valvecreation device 2516 having three wire-like structures 2517A, 2517B, and2517C for a resulting six contact portions located around thecircumference of the vessel wall, it should be understood that a valvecreation device in accordance with embodiments hereof may include agreater number or lesser number of wire-like structures andcorresponding sets of contact portions.

In the preset closed configuration valve creation device 316 has aresistance to opening that may depend on several factors in addition tothe resilient material from which it is formed, including materialstiffness of valve creation device 316, material thickness of valvecreation device 316, and/or the geometry of valve creation device 316.By manipulating these factors, valve creation device 316 may be designedto obtain an open configuration under select pressure gradients suchthat the valve creation device will open at a particular implantationsite within the vasculature. For example, a thinner wire-like structure317 is less stiff and therefore has less resistance to opening than athicker wire-like structure 317 of the same material. However, wire-likestructure 317 must have a sufficient thickness and closing force tocause the opposing vessel walls to be forced together. Stiffness refersto the resistance of an elastic body to deflection or deformation by anapplied force. In an embodiment, manufacturing or processing steps maybe employed in order to alter the stiffness, i.e., resistance todeflection or deformation of wire-like structure 317. For example, heattreatment or irradiation (for a polymer wire) may be employed to alterthe modulus of elasticity of the material of wire-like structure 317.

In embodiments hereof, magnets may be utilized to effect and/or enhanceclosure of a valve creation device in accordance herewith. For example,FIG. 6 shows a valve creation device 616 formed from a wire-likestructure 617, the device having a first leg 618, a second leg 622, anda curved connector 626 extending between the first and second legs.Alternatively, in an embodiment, first leg 618 and second leg 622 may beconnected together by a hinge (not shown). A first magnet 632 is locatedat a contact portion 619 of first leg 618 and a second magnet 634 islocated at a contact portion 623 of second leg 622. Magnets 632, 634 areoriented on wire-like structure 617 to be attracted to each another sothat contact portions 619, 623 firmly press together in the closedconfiguration of valve creation device 616 shown in FIG. 6 and onceimplanted with valve creation device 616 within a vein will operablyforce opposing portions of the vessel wall of the vein together. Valvecreation device 616 holds the opposing portions of the vein wall forcedtogether in the absence of a pressure differential while sufficientantegrade blood flow will operate to push apart first and second legs618, 622 of valve creation device 616 by exceeding the magnetic force ofmagnets 632, 634. In one embodiment, magnets 632, 634 may range indiameter between 0.5 mm to 2.5 mm in diameter, may have a thickness lessthan 0.125 inches or 3.175 mm, and have a magnetic force between 0.0182to 0.0455 lbs. Magnets 632, 634 may be positioned on wire-like structure617 to abut extravascularly or intravascularly when the valve creationdevice is implanted in vivo. If placed intravascularly, magnets 632, 634may be coated or covered with a biocompatible material such as parylene.Magnets 632, 634 may be attached to wire-like structure 617 by abiocompatible adhesive or other suitable attachment mechanism. In thedescribed embodiment, magnets 632, 634 alone function to pull legs 618,622 together and close valve creation device 616. In another embodiment,magnets 632, 634 may be used on valve creation device 316 describedabove such that biasing member 326 aids in closing, or on any valvecreation device of a resilient material using a biasing member describedbelow, to enhance closure thereof.

In another embodiment, closure of the vessel lumen by a valve creationdevice may be enhanced via the use of expandable loops on the valvecreation device that increase surface contact or coverage on the outersurface of the vein wall to operably push more vein tissue together.FIG. 7 shows a side view of a valve creation device 716 having a firstleg 718, a second leg 722, and a biasing member 726 attached to andextending between the first and second legs. Sharpened or pointed tips728, 730 at the ends of first and second legs 718, 722, respectively areused to pierce and penetrate through opposing portions of the vesselwall of the vein. Rather than straight linear contact portions as shownabove in the embodiment of FIG. 3, first and second legs 718, 722include expandable loops 736, 738, along respective end portions 720,724 thereof, which define diamond-shaped contact portions 719, 723. Asshown in FIGS. 8A and 8B, which illustrate valve creation device 716implanted within a vein 700, expandable loops 736, 738 cover a greatersurface area on the outer surface of the vein wall so that contactportions 719,723 operably push more tissue together and enhance thebackflow prevention of vein creation device 716. As such the clamping orpinching force of expandable loops 736, 738 is distributed along agreater surface area of the vessel wall. Expandable loops 736, 738 areformed of a superelastic or resilient material that self-expands to itspreset memory configuration after delivery and deployment of valvecreation device 716 within vein 700. During delivery within vein 700,expandable loops 736, 738 would be straightened into a deliveryconfiguration by a retractable delivery sheath or other mechanism. Oncepositioned at the treatment site, valve creation device 716 is deployedand expandable loops 736, 738 pass through the vessel wall of vein 700after respective pointed tips 728, 730 create an opening or passagewaythere through. During this initial implantation step, the vessel wall ofvein 700 straightens or compresses expandable loops 736, 738 such thatthey can be passed there through.

In another embodiment, closure of the vessel lumen within the vein maybe enhanced via the use of multiple fingers that extend from each leg ofthe valve creation device and operate to grab the outer surface of thevessel and force opposing portions of the vein wall inwardly. Moreparticularly, FIG. 12 shows a valve creation device 1216 in its presetclosed configuration formed from a wire-like structure 1217 of aresilient material, the device having a first leg 1218, a second leg1222, and a biasing member 1226 extending between the first and secondlegs. As best shown in FIG. 13A, a set of two curved extensions orfingers 1237A, 1237B extend outwardly in opposite directions from adistal end 1235 of first leg 1218 in a plane perpendicular to alongitudinal axis L_(A) of valve creation device 1216. Finger 1237A hasa distal end 1233A, and finger 1237B has a distal end 1233B. Duringdelivery within a vein, fingers 1237A, 1237B may be straightened into adelivery configuration by a retractable delivery sheath or othermechanism. Once positioned at the treatment site, valve creation device1216 is deployed and fingers 1237A, 1237B pass through the vessel wallof the vein. During this initial implantation step, the vessel wall ofthe vein maintains fingers 1237A, 1237B in the straightened deliveryconfiguration such that they can be passed there through. Once distalend 1235 of first leg 1218 passes through the vessel wall, fingers1237A, 1237B self-expand to their preset memory configuration and wraparound the outer surface of the vein, as best illustrated in thecross-sectional view of FIG. 13, which shows valve creation device 1216in the open configuration implanted within vein 1300. As such, fingers1237A and 1237B extend around and press against a substantial portion ofthe vessel wall. Similarly, a set of two curved extensions or fingers1239A, 1239B extend outwardly in opposite directions from a distal end1241 of second leg 1222 in a plane perpendicular to longitudinal axisL_(A) of valve creation device 1216. Finger 1239A has a distal end1243A, and finger 1239B has a distal end 1243B. During delivery within avein, fingers 1239A, 1239B may be straightened into a deliveryconfiguration by a retractable delivery sheath or other mechanism. Oncepositioned at the treatment site, valve creation device 1216 is deployedand fingers 1239A, 1239B pass through the vessel wall of the vein.During this initial implantation step, the vessel wall of the veinmaintains fingers 1239A, 1239B in the straightened deliveryconfiguration such that they can be passed there through. Once distalend 1241 of second leg 1222 passes through the vessel wall, fingers1239A, 1239B self-expand to their preset memory configuration and wraparound the outer surface of the vein. As such, fingers 1239A and 1239Bextend around and press against a substantial portion of the vesselwall.

Thus, as shown in the cross-sectional view of FIG. 13, fingers 1237A,1237B, 1239A, and 1239B collectively extend around and press against asubstantial portion of the outer circumference of the vein wall. Eachfinger acts to push the vessel wall inwards to close the lumen of thevein when valve creation device 1216 returns to the preset closedconfiguration shown in FIG. 12. More particularly, as indicated by thedirectional arrows in phantom on FIG. 13, distal end 1233A of finger1237A and distal end 1233B of finger 1237B operate as a first set ofcontact portions of valve creation device 1216 that are biased orpressed toward each other to press opposing portions of the vessel walltogether when valve creation device 1216 is in the preset closedconfiguration. Similarly, distal end 1243A of finger 1239A and distalend 1243B of finger 1239B operate as a second set of contact portions ofvalve creation device 1216 that are biased or pressed toward each otherto press opposing portions of the vessel wall together when valvecreation device 1216 is in the preset closed configuration. Further,distal end 1235 of first leg 1218 and distal end 1241 of second leg 1222operate as a third set of contact portions of valve creation device 1216that are biased or pressed toward each other to press opposing portionsof the vessel wall together when valve creation device 1216 is in thepreset closed configuration. Collectively, the vessel wall is forcedtogether in multiple locations which may more completely close the lumenof the vein, thereby enhancing backflow prevention through the newlycreated valve.

FIG. 9 illustrates a portion of a valve creation device 916 inaccordance with another embodiment hereof for minimizing the risk ofblood leaking through the vein wall after the valve creation device isimplanted. To prevent extravascular leakage of blood through thepoint(s) at which valve creation device 916 passes through the vesselwall, a seal 944 is attached to wire-like structure 917. Seal 944 may beof any suitable material such as an elastomeric material, a natural orsynthetic rubber, silicone, or a collagen foam plug. Seal 944 may beattached to wire-like structure 917 by a biocompatible adhesive or othersuitable attachment mechanism. Seal 944 acts to press against one ormore surface(s) of the vessel wall after pointed tip 928 of wire-likestructure 917 pierces through the vein wall. In the embodiment of FIG.9, seal 944 has a dumbbell configuration with an intermediate portion945, which has a first or reduced diameter, being sandwiched between endportions 929A, 929B, which have a second or flared diameter that isgreater than the first or reduced diameter of intermediate portion 945.When placed in situ, intermediate portion 945 will extend through thevessel wall with end portion 929A pressing or sitting against the outersurface of the vessel wall and end portion 929B pressing or sittingagainst the inner surface of the vessel wall. In an embodiment (notshown), the seal may have an annular or donut-shaped configurationsimilar to an O-ring or washer. The annular seal would be attached tothe wire-like structure 917 in a location such that it is locatedagainst the inner surface of the vessel wall or the outer surface of thevessel wall when placed in situ.

Another embodiment of a valve creation device 1016 is shown in FIGS.10-11. Valve creation device 1016 acts as a support framework to openand close opposing portions of the vessel wall of a vein in response toantegrade and retrograde blood flow to thereby mimic venous valveoperation for treating chronic venous insufficiency. Similar to theabove embodiments, valve creation device 1016 is an implantableprosthesis formed from a wire-like or tubular structure 1017 of aresilient material and includes a first leg 1018, a second leg 1022, anda biasing member 1026 extending between first leg 1018 to second leg1022. In this embodiment, the legs 1018, 1022 of valve creation device1016 are each configured to engage the vessel wall of the vein with aset of attachment joints. First leg 1018 has a first attachment joint1020 and a third attachment joint 1021 separated by a curved segment1013 defining a contact portion 1019, and second leg 1022 has a secondattachment joint 1024 and a fourth attachment joint 1025 separated by acurved segment 1013 defining a contact portion 1023, each of attachmentjoints 1020, 1021, 1024, 1025 is configured to engage the vessel wall ofthe vein. In one embodiment, attachment joints 1020, 1021, 1024, 1025include anchors attached to wire-like structure 1017 that lodge withinthe vessel wall to securely fix valve creation device 1016 within thevein. The anchors embed midway through the vessel wall, such as throughsome or the entire intimal layer and some or the entire medial layer ofthe vein wall, rather than penetrate there though. The anchors avoidpenetrating through the vessel wall to minimize the risk of bloodleaking through the vein wall. Although the anchors are illustrated assmooth surfaced round balls in FIGS. 10-11, the anchors may includepointed or spiked barbs or tines such as those depicted in FIGS. 21-24,or may have other configurations suitable for lodging within the vesselwall. In another embodiment, the anchors penetrate through the vesselwall to increase pulling or pinching the vein wall together. In additionto securing valve creation device 1016 in the vein, the anchorssimultaneously act as a sealing mechanism to prevent blood loss throughthe penetrated vessel wall.

Valve creation device 1016 is operable to alternate between a presetclosed configuration that in vivo results in the valve closedconfiguration shown in FIG. 10 and an open configuration that in vivoachieves the valve open or flow configuration shown in FIG. 11. In thepreset closed configuration, first attachment joint 1020 is biasedtoward third attachment joint 1021 on first leg 1018 and secondattachment joint 1024 is biased toward fourth attachment joint 1025 onsecond leg 1022 such that first leg contact portion 1019 is biasedtoward and/or contacts second leg contact portion 1023. However, valvecreation device 1016 is deployed within a vein 1000 in its openconfiguration, such that attachment joints 1020, 1021, 1024, and 1025engage the vessel wall of vein 1000 as shown in FIG. 11. The delivery ofvalve creation device 1016 is described in further detail below withrespect to FIGS. 21-24. After valve creation device 1016 is releasedfrom the delivery system, it reverts back to its preset closedconfiguration shown in FIG. 10 due to the restoring spring force ofwire-like structure 1017. As valve creation device 1016 closes,attachment joints 1020 and 1021 located along first leg 1018 move towardeach other causing vein wall segment 1046 to fold inwardly toward theopposing vein wall. Similarly, attachment joints 1024 and 1025 locatedalong second leg 1022 move toward each other causing vein wall segment1047 to fold inwardly toward the opposing vein wall. As noted above,contact portion 1019 of first leg 1018 and contact portion 1023 ofsecond leg 1022 also move toward each other as valve creation device1016 returns to the preset closed configuration. Vein wall segment 1046and vein wall segment 1047 are thereby pushed together until contactportion 1019 of first leg 1018 and contact portion 1023 of second leg1022 abut as shown in FIG. 10, such that the lumen of the vein issubstantially closed. The restoring force of valve creation device 1016due to the resilient material of wire-like structure 1017 thus drawsvein wall segments or flaps 1046, 1047 together to create a new valvewithin the vein. In situ, antegrade blood flow acts to forcibly separatecontact portion 1019 of first leg 1018 and contact portion 1023 ofsecond leg 1022 to achieve the valve open configuration shown in FIG. 11and to allow flow through the new valve. When blood flow through thevein changes direction, i.e., retrograde blood flow occurs due tochanging pressure differentials across the new valve, valve creationdevice 1016 reverts back to the preset closed configuration to therebyreturn the new valve to the valve closed configuration and prevent bloodfrom backflowing through the new valve.

In an embodiment, valve creation device 1016 extends longitudinallywithin the vein such that attachment joints 1020, 1021, 1024, 1025 arein the same longitudinal plane when valve creation device 1016 isimplanted within the vein. In another embodiment, attachment joints 1020and 1024 extend within a first longitudinal plane when valve creationdevice 1016 is implanted within the vein, and attachment joints 1021 and1025 extend within a different longitudinal plane. Further, in anotherembodiment (not shown), the valve creation device may include two ormore wire-like structures, each having closed and open configurationssimilar to wire-like structure 1017 as described above, that areoriented such that additional sets of contact portions are locatedaround the circumference of the vein. Multiple sets of contact portionspositioned around the circumference of the vein may result in morecomplete closure of the vein lumen when the opposing portions of thevessel wall are forced or gathered together. For example, in anembodiment a valve creation device may include a first wire-likestructure 1017 and a second wire-like structure 1017 having anorientation rotated approximately ninety degrees from the firstwire-like structure 1017, with the first and second wire-like structuressecured together at a single overlapping point or apex on biasingmembers 1026.

The valve prostheses described herein are preferably delivered in apercutaneous, minimally invasive manner and may be delivered by anysuitable delivery system. Referring now to FIGS. 14-17, a method ofpercutaneously placing a valve creation device within a vein to create avalve from autologous vein tissue according to an embodiment hereof isdescribed. Lumenal access to the venous vasculature is obtained usingstandard percutaneous techniques, such as the Seldinger technique aswould be understood by one of ordinary skill in the art. Access to thevasculature may be achieved through a branch of the femoral vein, oralternatively, may be achieved through a branch of a peripheral vein,such as but not limited to the subclavian vein, the popliteal vein, orthe greater saphenous vein. A guidewire (not shown) is maneuvered to atreatment site within vein 1400 where a new valve is to be created. Thetreatment site may be located upstream or downstream of leaflets of aninsufficient native valve. Valve prostheses described herein may bedelivered to the treatment site in an antegrade or retrograde manner. Inone embodiment, delivery of the valve creation device is in an antegradedirection such that the valve creation device passes forwardly throughnative valves located within the vein in route to the treatment site. Aballoon catheter 1450 with valve creation device 316, as described abovewith reference to FIG. 3, mounted thereon is loaded into a retractablesheath 1448 that surrounds and substantially straightens the valvecreation device 316, which eases advancement thereof through thevasculature to the treatment site within a body vessel. Sheath 1448,balloon catheter 1450 and valve creation device 316 are then trackedover the guidewire through the vasculature to the treatment site, asshown in FIG. 14. Retractable sheath 1448 is movable in a longitudinaldirection along and relative to balloon catheter 1450 and extends to aproximal portion of the delivery system where it may be controlled viaan actuator (not shown), such as a handle. When the actuator isoperated, retractable sheath 1448 is proximally retracted over catheter1450.

Valve creation device 316 may be secured to balloon 1452 with aconnector 1454. Connector 1454 may be a breakable restraining memberthat uncouples the valve creation device 316 when balloon is inflated toa predetermined diameter. The breakable restraining member may be formedfrom an elastomeric material such as polyurethane or pelethane and mayinclude a perforation or line of weakness 1456 that would cause theelastomeric material to split in a preferred direction when balloon 1452reaches a particular diameter. The breakable restraining member may bean annular ring or straight band that is placed over valve creationdevice 316 mounted on balloon 1452, and is attached to balloon 1452 inat least one spot to prevent the breakable restraining member fromdislodging and/or embolizing from balloon 1452 after valve creationdevice 316 is deployed. In another embodiment, connector 1454 may be anannular or straight thin metal element that holds valve creation device316 onto balloon 1452 until a current is applied to dissolve the thinmetal element, thereby releasing valve creation device 316 from balloon1452 with an electrolytic detachment technique. The thin metal elementmay or may not include a line of weakness 1456. Electrolytic detachmenttechniques are known, for example, for delivering and detaching coils atan occlusion or aneurysm site. Thin metal elements and detachmenttechniques therefore that may be adapted for use in embodiments hereofare described in U.S. Pat. Nos. 5,569,245 to Guglielmi et al. and5,624,449 to Pham et al., which are incorporated by reference herein intheir entirety.

Once valve creation device 316 is properly positioned and it is desiredto deploy valve creation device 316, sheath 1448 and valve creationdevice 316 may be moved relative to each other such that valve creationdevice 316 is released from sheath 1448 and allowed to assume its presetconfiguration as shown in FIG. 15. To cause the relative motion betweensheath 1448 and valve creation device 316, valve creation device 316 maybe distally advanced while sheath 1448 is held in place so that valvecreation device 316 is essentially pushed out of the distal exit port ofsheath 1448, or sheath 1448 may be retracted in a proximal directionwhile valve creation device 316 is held in place so that valve creationdevice 316 is essentially exposed, or a combination thereof. Once valvecreation device 316 exits sheath 1448, the ends of valve creation device316 elastically flare open and assume a curve as valve creation device316 returns to its preset closed configuration due to the inherentspring restorative force of the valve creation device.

Balloon 1452 is then at least partially inflated to push pointed tips328, 330 of valve creation device 316 into and through the vessel wallas shown in FIG. 16 and to position contact portions 319, 323 against anouter surface of the vessel wall of vein 1400 as shown in FIG. 17. If abreakable restraining member is used as connector 1454 to secure valvecreation device 316 to balloon 1452, inflation of the balloon 1452 to apredetermined diameter will break apart or open connector 1454 alongline of weakness 1456 thereby uncoupling valve creation device 316 fromballoon 1452 as shown in FIG. 16. Alternatively, a thin dissolvablemetal element is used as connector 1454 to secure valve creation device316 to balloon 1452, a current is applied to dissolve the thin metalelement and thereby uncouple valve creation device from balloon 1452(not shown).

Once the valve creation device 316 is fixed to opposing portions of thevessel wall of vein 1400 and valve creation device 316 is uncoupled fromballoon 1452, balloon catheter 1450 may be deflated and removed from thepatient. As described above with respect to FIG. 4, first contactportion 319 of valve creation device 316 engages the vessel wall at afirst location, and second contact portion 323 of valve creation device316 engages the vessel wall at an opposing location, or approximately180 degrees away from the first location. With balloon catheter 1450removed, valve creation device 316 reverts to its preset closedconfiguration thereby pulling the opposing portions of the wall of vein1400 together to substantially close the lumen of vein 1400 as shown inFIG. 17. In such a manner, percutaneously delivered valve creationdevice 316 utilizes autologous vein tissue to form a new valve byforcing together opposing portions of the vessel wall.

In an embodiment, vein 1400 is a deep vein that is surrounded in part bymusculature tissue. Prior to implanting valve creation device 316, theouter surface or circumference of the vein wall may be extravascularlyseparated from the muscle so that valve creation device 316 may operateto pull the vein wall together. Any suitable method may be utilized toseparate the vein wall from the surrounding musculature tissue. In oneexample, an inflatable balloon extravascularly placed between the veinwall and muscle may be expanded to dilate the space between the veinwall and the surrounding musculature tissue and cause the separationtherebetween.

In an embodiment shown in FIG. 14A, balloon 1452A may be tapered suchthat a proximal end portion 1451 has a larger diameter than a distal endportion 1453 when balloon 1452A is inflated. Omitted from FIG. 14A forclarity, valve creation device 316 is mounted on the smaller distal endportion 1453 of balloon 1452A. When inflated, the larger proximal end1451 of balloon 1452A operates to center the delivery device within thevein when valve creation device 316 is deployed. In another embodimentshown in FIG. 14B, the delivery device may include a second balloon 1458proximal to a balloon 1452B for centering the delivery device duringdeployment of valve creation device 316 (omitted from FIG. 14B forclarity), which is mounted on balloon 1452B as described above withrespect to balloon 1452 of FIG. 14.

Referring now to FIGS. 18-20, another method of percutaneously placing avalve creation device within a vein to create a valve from autologousvein tissue according to an embodiment hereof is described. In thisembodiment, valve creation device 316, as described above with referenceto FIG. 3, is mounted onto a distal end of a delivery catheter 1860.Referring to FIGS. 18, 18A and 18B, delivery catheter 1860 includes anelongated proximal trunk or tubular shaft 1862 having a proximal endthat may be attached to a luer or hub (not shown) and a distal endattached to first and second distal branches or arms 1864A, 1864B,respectively, via a junction 1869. First and second distal arms 1864A,1864B separately and independently extend from the distal end ofproximal shaft 1862. Junction 1869 is a transition area between proximalshaft 1862 and distal arms 1864A, 1864B. In one embodiment, proximalshaft 1862 and distal arms 1864A, 1864B may be separate components thatare welded, fused, bonded, or otherwise joined together. In anotherembodiment, if the same material is used for proximal shaft 1862 anddistal arms 1864A, 1864B, then catheter 1862 may be formed via extrusionresulting in one continuous structure. Each arm 1864A, 1864B has agenerally C-shaped or semicircular transverse cross-section along itslength, with an open area 1865A, 1865B of each C-shaped arm 1864A,1864B, respectively, being oriented outward as shown in FIG. 18A. FIG.18A is an end view of distal arms 1864A, 1864B of delivery catheter 1860having legs 318, 322 of valve creation device 316 loaded therein, withthe vein and delivery sheath removed for clarity. In an embodiment, theC-shaped cross-section of each arm 1864A, 1864B may be between 25% and75% of the circumference of a circle. Each arm 1864A, 1864B may belongitudinally tapered such that delivery catheter 1860 may bedisengaged after valve creation device 316 is deployed as will beexplained in more detail herein. For example, as shown in FIG. 18B, theproximal ends of each arm 1864A, 1864B are approximately 25% of a circlesuch that the top edge of the arm barely extends over valve creationdevice 316 and the C-shaped cross-section of each arm 1864A, 1864Bgradually increases until the distal ends of each arm 1864A, 1864B areapproximately 50% of a circle. In one embodiment shown in FIG. 18B,distal arms 1864A, 1864B may have a length that is shorter than legs318, 322 of valve creation device 316 loaded therein such that pointedtips 328, 330 extend beyond the distal ends of arms 1864A, 1864B,respectively. In another embodiment (not shown), distal arms 1864A,1864B may have a length that is approximately equal to or greater thanlegs 318, 322 of valve creation device 316 loaded therein. Distal arms1864A, 1864B are connected with a self-expanding spring element 1866that spans between arms 1864A, 1864B. Spring element 1866 may spanbetween a proximal portion, a middle portion, or a distal portion ofarms 1864A, 1864B.

At the distal end thereof, a top portion of proximal shaft 1862 has aconcave curved top edge 1861. Similarly, at the proximal ends thereof, aside portion of each distal arm 1864A, 1864B have a concave curved topedge 1863A, 1863B, respectively. Collectively, these carved out portionsform a side opening or port 1867 in catheter 1860 at junction 1869. Port1867 is in fluid communication with open areas 1865A, 1865B of C-shapeddistal arms 1864A, 1864B such that catheter 1860 has a continuous pathor track formed thereon, as will be described in more detail herein.Valve creation device 316 in its preset closed configuration is mountedwithin catheter 1860 such that legs 318, 322 of valve creation device316 are loaded through open areas 1865A, 1865B to sit against the outersurfaces of distal arms 1864A, 1864B, as best shown in the end view ofFIG. 18A, and such that biasing member 326 of valve creation device 316is positioned adjacent to or within port 1867, as best shown in theperspective view of FIG. 18B.

With reference to FIG. 18, catheter 1860 with valve creation device 316mounted thereon are loaded into a retractable sheath 1848 that surroundsdistal arms 1864A, 1864B and compresses spring element 1866 to holdvalve creation device 316 in a delivery configuration, which easesadvancement thereof through the vasculature to the treatment site withina body vessel. Retractable sheath 1848 is movable in a longitudinaldirection along and relative to delivery catheter 1860 and extends to aproximal portion of the delivery system where it may be manipulated by aclinician to be proximally retracted over catheter 1860 when valvecreation device 316 is to be deployed. Sheath 1848 and catheter 1860with valve creation device 316 loaded thereon are percutaneouslyintroduced and delivered through the vasculature to the treatment siteas described above. The treatment site may be located upstream ordownstream of leaflets of an insufficient native valve.

Once valve creation device 316 is properly positioned, sheath 1848 ofthe delivery system is proximally retracted as shown in FIG. 19 todeploy valve creation device 316. Upon retraction of sheath 1448, distalarms 1864A, 1864B are released to swing open via self-expanding springelement 1866, which also pushes the pointed tips 328, 330 of valvecreation device 316 into and through the vessel wall as shown in FIG.19. After pointed tips 328, 330 have been deployed through the vesselwall, the compressed spring element 1866 continues to return to orresume its preset extended configuration shown in FIG. 19, which thencauses distal arms 1864A, 1864B to push the hooked end portions of valvecreation device 316 through the vessel wall such that contact portions319, 323 contact and eventually bear against the outer surface of thevessel wall as shown in FIG. 20. The restoring force of spring element1866 is stronger than the inherent spring force or mechanical memory ofvalve creation device 316 and is sufficient to deploy the device throughthe vessel wall. In an embodiment (not shown), catheter 1860 may includean inflatable balloon proximal to distal arms 1864A, 1864B for centeringthe delivery device during deployment of valve creation device 316.

Once legs 318, 322 of valve creation device 316 is fixed to opposingportions of the vessel wall of vein 1800, the catheter 1860 may beproximally retracted a short amount to disengage valve creation device316 therefrom. More particularly, legs 318, 322 of valve creation device316 may be disengaged from within distal arms 1864A, 1864B by slidingout of open areas 1865A, 1865B, respectively. Similarly, biasing member326 of valve creation device 316 may exit or be disengaged from withincatheter 1860 via port 1867. Proximal movement of catheter 1860 allowsbiasing member 326 to become disengaged by sliding over thelongitudinally tapered configuration of each arm 1864A, 1864B. Sincevalve creation device 316 is secured within the vessel via pointed tips328, 330 deployed through the vessel wall, the valve creation device 316remains stationary while catheter 1860 is proximally retracted andessentially is slid off the deployed valve creation device 316. Openareas 1865A, 1865B of the C-shaped distal arms 1864A, 1864B and port1867 thus collectively form an exit path or track that allows catheter1860 to be separated from the deployed valve creation device 316.

After the deployed valve creation device 316 is disengaged from catheter1860, sheath 1848 is then distally advanced to cover and re-constraindistal arms 1864A, 1864B therein so that catheter 1860 may be retractedand removed from the patient. With catheter 1860 removed, valve creationdevice 316 reverts to its preset closed configuration thereby pullingthe opposing portions of the wall of vein 1800 together to substantiallyclose the lumen of vein 1800 as shown in FIG. 20. In such a manner,percutaneously delivered valve creation device 316 thus utilizesautologous vein tissue to form a new valve by forcing together theopposing portions of the vessel wall.

FIGS. 21-24 illustrate the percutaneous delivery of valve creationdevice 1016, described above with reference to FIGS. 10 and 11.Referring to FIG. 21, balloon catheter 1450 with valve creation device1016 mounted thereon is loaded into retractable sheath 1448 thatsurrounds and substantially straightens the valve creation device 1016.As described above, the valve creation device may be secured to balloon1452 with a breakable restraining member (not shown) that uncouples thevalve creation device 1016 when balloon 1452 is inflated to apredetermined diameter, or with a thin metal element (not shown) thatholds the device until a current is applied to dissolve the thin metalelement. Sheath 1448, balloon catheter 1450 and valve creation device1016 are then tracked over the guidewire through the vasculature to atreatment site within a vein 1000.

Once valve creation device 1016 is properly positioned and it is desiredto deploy valve creation device 1016, sheath 1448 and valve creationdevice 1016 may be moved relative to each other such that a distalportion of valve creation device 1016 is exposed or released from sheath1448. As shown in FIG. 22, once valve creation device 1016 exits sheath1448 distal attachment joints 1020, 1024 flare open and extend to thevessel wall to return valve creation device 1016 to its presetconfiguration. Balloon catheter 1450 may be slightly proximallyretracted to secure attachment joints 1020, 1024 within the vessel wall.

Referring to FIG. 23, sheath 1448 is further retracted to expose theremainder of valve creation device 1016 and balloon 1452 is at leastpartially inflated to push proximal attachment joints 1021, 1025 ofvalve creation device 1016 into the vessel wall. Inflation of balloon1452 thus expands valve creation device 1016 into its openconfiguration. As noted above, valve creation device 1016 is uncoupledfrom balloon 1452, either by breaking apart the restraining member dueto the balloon inflation or by dissolving the thin metal element, andballoon catheter 1450 may then be deflated and removed from the patient.With balloon catheter 1450 removed, valve creation device 1016 revertsto its preset closed configuration shown in FIG. 24 due to the restoringspring force of valve creation device 1016 thereby drawing vein wallsegments or flaps 1046, 1047 together to substantially close the lumenof vein 1000.

Although the valve creation devices are described herein as configuredfor percutaneous placement, it should be understood that the valvecreation devices may alternatively be surgically implanted within a veinin a non-percutaneous manner and may be anchored to the vein in anysuitable manner, such as via sutures, clips, or other attachmentmechanisms.

As would be understood by one of skill in the art, an outside layer ofthe vein wall, called the adventitia, is made of collagen, vasa vasorumand nerve cells, whereas a middle layer of the vein wall, or media, ismade of smooth muscle cells and an inside layer of the vein wall, orintima, is made up of endothelial cells that provide a nonthrombogenicsurface for flowing blood. The inventors have found that the outside andmiddle layers of the vessel wall provide sufficient toughness foropposing portions of the vein wall to be forced together to form a newvalve by a valve creation device in accordance with embodiments hereofwithout tearing or ripping. Further it is believed that the anatomy ofthe vein wall has sufficient strength to enable opposing portions of thevein wall to act as a new valve by being capable of withstandingrepeated pulling apart and pushing together by a valve creation devicein accordance with embodiments hereof. In addition, a further advantageof an implanted valve creation device in accordance with embodimentshereof is that the intimal layer of the vessel wall forms theblood-contacting surfaces of the new valve.

While various embodiments according to the present invention have beendescribed above, it should be understood that they have been presentedby way of illustration and example only, and not limitation. It will beapparent to persons skilled in the relevant art that various changes inform and detail can be made therein without departing from the spiritand scope of the invention. Thus, the breadth and scope of the presentinvention should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the appendedclaims and their equivalents. It will also be understood that eachfeature of each embodiment discussed herein, and of each reference citedherein, can be used in combination with the features of any otherembodiment. All patents and publications discussed herein areincorporated by reference herein in their entirety.

1. An implantable prosthesis for creating a venous valve of autologoustissue, the prosthesis comprising: a valve creation device including atleast two contact portions that in a preset closed configuration forcesopposing portions of a vein wall together so that the opposing portionsof the vein wall are pressed together and sandwiched between the contactportions to substantially close a lumen of the vein and create a valveof autologous vein tissue to substantially prevent retrograde blood flowthrough the valve, wherein the valve creation device is configured tochange shape and assume a temporary open configuration in which thecontact portions and the opposing portions of the vein wall separate inresponse to antegrade blood flow through the vein to allow blood flowthrough the lumen of the vein.
 2. The prosthesis of claim 1, wherein theat least two contact portions comprise a first contact portion and asecond contact portion; wherein the valve creation device is a wire-likestructure having a first leg with the first contact portion, a secondleg with the second contact portion, and a segment extending between thefirst leg and the second leg and wherein the first and second contactportions are biased toward each other to operably force opposingportions of the vein wall together in situ so that the opposing portionsof the vein wall are pressed together and sandwiched between the contactportions to substantially close the lumen of the vein and create thevalve.
 3. The prosthesis of claim 2, wherein the valve creation deviceattains the open configuration that allows antegrade blood flow throughthe valve in response to a pressure gradient and wherein the valvecreation device returns to the preset closed configuration in theabsence of the pressure gradient to prevent retrograde blood flowthrough the valve.
 4. The prosthesis of claim 3, wherein the valvecreation device attains the open configuration that allows antegradeblood flow through the valve in response to a pressure gradient between2 mmHg and 25 mmHg.
 5. The prosthesis of claim 2, wherein the segmentextending between the first leg and the second leg is a biasing memberhaving spring characteristics to press together the contact portions ofthe first and second legs of the valve creation device.
 6. Theprosthesis of claim 5, wherein the biasing member is a U-shaped curveand the first and second legs of the valve creation device are mirrorimages of each other.
 7. The prosthesis of claim 5, wherein the biasingmember includes an elongated straight member operable to span across thevessel lumen of the vein.
 8. The prosthesis of claim 2, wherein thesegment extending between the first leg and the second leg is integrallyformed with the first and second legs such that the valve creationdevice is a unitary structure formed from a single piece of material. 9.The prosthesis of claim 2, wherein the first and second legs each have apointed tip for piercing the vein wall.
 10. The prosthesis of claim 9,wherein each pointed tip is at an end of a respective curved end portionof the first and second legs.
 11. The prosthesis of claim 2, wherein atleast one of the first leg or the second leg includes a seal attachedthereto, wherein the seal is operative to prevent leakage through thevein wall.
 12. The prosthesis of claim 11, wherein the seal has adumbbell configuration with an intermediate portion having a firstdiameter sandwiched between end portions having a second diametergreater than the first diameter of the intermediate portion, wherein theintermediate portion is operable to extend through the vessel wall andthe end portions sit against outer and inner surfaces of the vein wall.13. The prosthesis of claim 2, wherein the valve creation deviceincludes at least two wire-like structures that are secured together ata single overlapping point on the segments extending between the firstlegs and the second legs.
 14. The prosthesis of claim 2, wherein a firstmagnet is attached to the first leg and a second magnet is attached tothe second leg and wherein the magnets are oriented to be attracted toone another with a magnetic force sufficient to force the opposingportions of the vein wall together in situ to create the valve.
 15. Theprosthesis of claim 2, wherein the first and second contact portions ofthe first and second legs are self-expanding loops located alongrespective end portions of the first and second legs.
 16. The prosthesisof claim 2, wherein the first leg has two curved fingers that extend inopposite directions from an end thereof and the second leg has twocurved fingers that extend in opposite directions from an end thereof,wherein the curved fingers are substantially perpendicular to alongitudinal axis of the valve creation device.